Try teething rings... Mine sucks on my hand,bites random stuff(sometimes my hand)...funandfunction.com has lots of sensory sensitive chewies,blankets, clothing ect..hope this helps

sensory fidget toys you can buy from amazon sensory key in and there should be some safe alternatives

To grandma re sucking and chewing his shirt--our guy did that too and now he wears a chewy which you can order online from any place that is Autism and other Disability related, and the chewys are not expensive--they are fabric and worn around the neck so they can chew that instead of their shirt.At the moment , I can't give you any specific place, I have to go back in my records. I am a grandma too. I have an elastic band from physical therapy used for shoulder and knee exercises. I decided to hold one end while "GUY" held the other, because I wanted to know if he knew how to pull. So we both tugged, and i decided to let go to see what his reaction would be--I was a bit scared... so I let go and he heard the snap--and he smiled!! i rack my brain trying to think of ways i can help him, or relate to him. Once I tried going on the floor to be at his level so he did not have to look up so much. He seemed to enjoy that., so best wishes for you and your grandson.

Ha ha. My 3yrs old has started doing the same. There are days he is totally saturated from it and I am changing his shirt as he hate the wet feeling from it. I think I have chosen to ignore it as it could be worse. He was bitting himself before he started doing this, so I guess its a win for me as the bitting himself has stopped. OT has said it is to do with deep pressure in the mouth and they fimd it calming. So in my mind calming is good

thank you so much for the advice, I'm learning about everything with my wonderful grandson.